Affiliation of Author(s):自动化学院

Journal:Diangong Jishu Xuebao

Abstract:The method of traditional optical emission spectroscopy is not suitable for the quantitative measurements of the density of OH radical and O atom in low temperature plasma jets at atmospheric pressure. Thus, this paper applied the single-photon laser induced fluorescence (LIF) and two-photon absorption laser induced fluorescence (TALIF). The plasma jet with needle-cylinder electrode structure was excited by nanosecond pulsed power supply. (1)OH radical and O atom in the plasma jet have a lifetime of 1 ms and 3ms, respectively. They are much longer than the duration time of pulse discharge. (2)By fitting the decay curve of fluorescence intensity of OH radical vs time, the absolute density of OH radical is estimated to be 1012~1013cm-3. (3)The densities of both active species decrease monotonically with the increase of the axial distance along the jet. However, it's surprising to observe that there are still a large amount of active species at even several cm far away from the jet nozzle. (4)The increased excitation frequency and pulse voltage result in the increased density of active species. Moreover, with the increase of the concentration of H2O impurities in helium gas, OH radical density decreases after reaching a maximum value at 2.7×1013cm-3for H2O concentration of 120 ppm. The behavior of O atom density shows the same tendency with the increase of O2percentage in helium. The inflection point corresponding to the peak density of O atom occurs at the O2percentage of 0.5%. This study provides an important scientific basis for regulation and optimization of the densities of OH radicals and O atom in low temperature plasma jets. © 2017, The editorial office of Transaction of China Electrotechnical Society. All right reserved.

ISSN No.:1000-6753

Translation or Not:no

Date of Publication:2017-04-25

Co-author:董熙,裴学凯,岳远富,卢新培

Correspondence Author:Shuqun Wu